1. Field of the Invention
The present invention relates to a constituent substrate for electronic equipment and electronic equipment using the same, particularly to a constituent substrate for electronic equipment comprising a wiring layer made of copper, and a transparent conductive layer made of a composite oxide comprising indium oxide and a metal oxide as main components.
2. Description of the Related Art
Aluminum as a wiring material has the advantage of low resistance, and is widely used for wiring, electrodes, etc. on a substrate. For a transparent conductive layer used as a transparent electrode or the like, indium tin oxide (abbreviated to xe2x80x9cITOxe2x80x9d hereinafter) is generally used.
FIG. 6 is a schematic drawing showing a thin film transistor portion of a general thin film transistor type liquid crystal display device as an example of electronic equipment.
A thin film transistor 82 comprises a gate electrode 84 provided on a substrate 83, and a gate insulation film 85 provided to cover the gate electrode 84. A semiconductor active film 86 made of amorphous silicon (abbreviated to xe2x80x9ca-Sixe2x80x9d hereinafter) is provided on the gate insulation film 85 above the gate electrode 84, and a source electrode 88 and a drain electrode 89 are provided on the semiconductor active film 86 and the gate insulation film 85 through ohmic contact layers 87 made of amorphous silicon (abbreviated to xe2x80x9cn+ type a-Sixe2x80x9d hereinafter) containing n-type impurities such as phosphorus or the like over the region ranging from the semiconductor active film 86 to the gate insulation film 85. In addition, a passivation film 90 is provided to cover the thin film transistor 82 comprising the source electrode 88, the drain electrode 89, the gate electrode 84, etc., and a contact hole 91 is provided in the passivation film 90 above the drain electrode 89. Furthermore, a pixel electrode 92 made of ITO and electrically connected to the drain electrode 89 through the contact hole 91 is provided.
Also the sectional structure of a gate terminal pad 93 at the gate wiring end located outside the display region is shown on the left side of FIG. 6. A contact hole 95 is provided above a lower pad layer 94 made of a gate wiring material on the substrate 83 so as to pass through the gate insulation film 85 and the passivation film 90, and an upper pad layer 96 comprising the same transparent conductive layer as the pixel electrode 92 is provided to be electrically connected to the lower pad layer 94 through the contact hole 95. The structure at the source wiring end is also similar to the above-described structure.
As described above, for example, in a thin film transistor, a transparent conductive layer which constitutes the gate terminal, the source terminal, and pixel electrodes, and a wiring metal which constitutes gate wiring, source wiring and the drain electrode are arranged in direct connection to each other.
However, when ITO is used as the transparent conductive layer of electronic equipment, and aluminum is used as the wiring metal, direct contact between ITO and aluminum causes oxidation of aluminum by oxygen contained in ITO, thereby causing the problem of increasing the electric resistance value of the contact portion.
In consideration of the above-described point, it is an object of the present invention to provide a constituent substrate for electronic equipment using a wiring layer made of a material which causes no increase in electric resistance value of a contact portion even in contact with a transparent conductive layer of ITO or the like, and electronic equipment using the constituent substrate.
A constituent substrate for electronic equipment of the present invention uses a wiring layer made of copper, and a transparent conductive layer made of a composite oxide comprising indium oxide and an oxide of at least one metal selected from the group consisting of zinc, tin, gallium, thallium, magnesium, and lead.
Aluminum and copper have resistivity of 2.7 xcexcxcexa9/cm and 1.6 xcexcxcexa9/cm, respectively, and thus have sufficiently low resistivity as compared with other metals. However, for example, direct connection between aluminum and ITO has a contact resistance of about 103 xcexa9cm2, while direct connection between copper and ITO has a contact resistance of about 10xe2x88x927 xcexa9cm2. There is thus a large difference in contact resistance.
Namely, even when the composite oxide used for the transparent conductive layer and comprising indium oxide and an oxide of at least one metal selected from the group consisting of zinc, tin, gallium, thallium, magnesium, and lead is brought into direct contact with copper used for the wiring layer, the electric resistance value of the contact portion is not increased.
Zinc, tin, gallium, thallium, magnesium, and lead are all elements having transparency and conductivity when oxides thereof form composite oxides with indium oxide. Of these composite oxides, indium zinc oxide is preferably used in the present invention. This is because some of the composite oxides probably cause etching of copper wiring with an etchant used for etching a composite oxide material. However, the copper wiring is not affected by about 0.5 to 5% diluted hydrochloric acid or oxalic acid aqueous solution, which is an etchant for indium zinc oxide. Therefore, in the use of copper as the material for the wiring layer, indium zinc oxide is preferably used as the material for the transparent conductive layer.
The constituent substrate for electronic equipment of the present invention comprises the wiring layer and the transparent conductive layer which are electrically connected.
In this case, the wiring layer and the transparent conductive layer may be brought into direct contact or indirectly contact with a conductor held therebetween.
Electronic equipment of the present invention comprises the above-described constituent substrate for electronic equipment. Examples of electronic equipment using a transparent electrode layer include a thin film transistor type liquid crystal display device, a solar cell, an electroluminescence device, a touch panel, etc. because the transparent electrode layer can be used as an electrode or the like which transmits light.
The electronic equipment comprising the constituent substrate for electronic equipment comprising low-resistance wiring made of copper, and the transparent conductive layer made of a composite oxide containing, as main components, indium oxide and an oxide of at least one metal selected from the group consisting of zinc, tin, gallium, thallium, magnesium, and lead has the following advantages. The electronic equipment can comply with increases in;the area and definition, has excellent performance uniformity and reliability, and can be manufactured by a simple process without the need to insert a barrier metal for decreasing contact resistance between the wiring and the transparent conductive layer, with no wiring defect. and high yield.